1. Field of the Invention
The present invention is in the field of wire fasteners and more particularly to terminal fasteners for use with non-malleable wire.
2. Description of the Prior Art
Many wire fasteners are available in the prior art. The majority of prior art fasteners are for malleable wire such as copper. Some such fasteners include a pair of foldable members which are pressed down around the wire to hold it in place and may include a terminal member such as a loop which may be positioned around a binding post, bolt or other such device connected to a circuit to which connection is desired to be made. Stainless steel fasteners are often preferred to provide a strong long lasting and corrosion resistant fastener that makes good electrical contact. Generally, the wire is caused to deform around a portion of the stainless steel fastener to prevent slippage.
Such fasteners encounter difficulties when they are applied to a non-malleable wire such as tungsten since the non-malleable wire does not deform to provide a non-slipping connection to the fastener. Thus, when it is required that the wire be able to withstand axial forces or pull, the wire can slip out of the fastener and electric contact will be broken. Techniques such as welding are complicated and quite costly.
Although the present invention has utility for providing fasteners with various types of wire, the primary utility is intended for providing an electrical fastener for use with a non-malleable wire such as 0.008-inch tungsten, which can resist an axial pull of at least eight pounds without breaking contact. This is accomplished using simple production equipment to minimize cost and maximize ease of manufacture. Specifically, a double xe2x80x9cSxe2x80x9d shaped or xe2x80x9ccamel backxe2x80x9d shaped mechanical attachment along the axis of the wire is used with the wire being crimped on either side thereof. To assure further pull resistance, the wire is passed in xe2x80x9ccamel backxe2x80x9d fashion over a hump formed by a folded-over spring member which has small burrs that grip the wire at the contact points and the wire is forced perpendicular to its length against the burrs aided by the spring force of the spring member to significantly increase the contact force of the wire against the spring member. The ears that are folded over the wire and crimped on either side of the hump are positioned relatively close to the hump to cause a tight bend in the wire around the hump and thus force it into the double xe2x80x9cSxe2x80x9d shape that allows the assembly to resist separation even when extremely high axial pull forces are applied. The two pairs of ears are an integral part of the terminal and located directly across from each other. In order to prevent overlapping of the ears when folded, they may be shaped with, for example, a forty-five degree angle, so that when folded and crimped, the forty-five degree edges are close but not overlapping each other. The meshing reduces the leverage distance from the captured wire to the fold of each ear which results in greater force required to lift the ears away from the terminal body thus an increase of the resistance to pulling force and improving the overall wire to terminal axial pull strength.